Not Applicable
This invention relates generally to a method of inhibiting angiogenesis associated with the hyperproliferation of malignant cells, and in particular, to the use of active forms of vitamin D to inhibit angiogenesis of malignant cells.
Extensive research during the past two decades has established important biologic roles for vitamin D apart from its classic role in bone and mineral metabolism. Specific nuclear receptors for 1xcex1,25-dihydroxyvitamin D3, the hormonally active form of vitamin D, are present in cells from diverse organs not involved in calcium homeostasis. For example, specific, biologically active vitamin D receptors have been demonstrated in the human prostatic carcinoma cell line, LNCaP, (Miller et al., 52 Cancer Res. (1992) 515-520); Vitamin D receptors have also been described for many other neoplastic cells, e.g., carcinomas of the breast and the colon.
It has been reported that certain vitamin D compounds and analogues are potent inhibitors of malignant cell proliferation and are inducers/stimulators of cell differentiation. For example, U.S. Pat. No. 4,391,802 issued to Suda et al. discloses that 1xcex1-hydroxyvitamin D compounds, specifically 1xcex1,25-dihydroxyvitamin D3 and 1xcex1-hydroxyvitamin D3, possess potent antileukemic activity by virtue of inducing the differentiation of malignant cells (specifically leukemia cells) to nonmalignant macrophages (monocytes), and are useful in the treatment of leukemia. Antiproliferative and differentiating actions of 1xcex1,25-dihydroxyvitamin D3 and other vitamin D3 analogues have been reported with respect to cancer cell lines. More recently, an association between vitamin D receptor gene polymorphism and cancer risk has been reported, suggesting that vitamin D receptors may have a role in the development, and possible treatment, of cancer.
These previous studies have focused exclusively on vitamin D3 compounds. Even though these compounds may indeed be highly effective in promoting differentiation in malignant cells in culture, their practical use in differentiation therapy as anticancer agents is severely limited because of their equally high potency as agents affecting calcium metabolism. At the levels required in vivo for effective use as, for example, antileukemic agents, these same compounds can induce markedly elevated and potentially dangerous blood calcium levels by virtue of their inherent calcemic activity. That is, the clinical use of 1xcex1,25-dihydroxyvitamin D3 and other vitamin D3 analogues as anticancer agents is precluded, or severely limited, by the risk of hypercalcemia.
Cancerous cells derive from a single cell that has mutated in a way that permits it to escape from the biochemical controls that limit the multiplication of normal cells. Once that cell fails to respond normally to growth inhibitors, it starts to proliferate. When the growing tumor reaches a certain diameter, however, simple diffusion in and out of the tumor tissue no longer suffices to supply oxygen and nutrients and remove waste. Further growth depends on angiogenesis (i.e., the formation of new blood vessels from the existing vascular bed), and the small tumor must produce factors that stimulate the growth of blood vessels. Therefore, the inhibition of angiogenesis, in turn leads to the decrease of proliferation of malignant and neoplastic cells.
Vascular endothelial growth factor (VEGF) is a key mediator of angiogenesis. This growth factor stimulates the endothelial cell proliferation, sprouting, migration and morphogenesis. A recent study has found that 1xcex1,25-dihydroxyvitamin D3 significantly inhibited vascular endothelial growth factor (VEGF)-induced endothelial cell proliferation. (See xe2x80x9c1xcex1,25-Dihydroxyvitamin D3 Ihibits Angiogenesis In Vitro and In Vivoxe2x80x9d, Mantell, D. J., Owens, P. E., Bundred, N. J., Mawer, E. B., Canfield, A. E., Circulation Research, Aug. 4, 2000, pp. 214-220. Incorporated herein by reference). It was also demonstrated that 1xcex1,25-dihydroxyvitamin D3 induced the regression of sprouting elongated endothelial cells, where the regression was due to the induction of apoptosis within the cell population. As mentioned earlier however, use of such vitamin D3 analogs as anticancer agents is limited due to the inherent calcemic activity of the compounds. Therefore a need exists for compounds with the ability to inhibit angiogenesis of malignant cells but which have less calcemic activity.
The present invention provides a method of inhibiting angiogenesis associated with malignant cells. The method includes use of hypocalcemic active vitamin D compounds to inhibit angiogenesis. The present invention also provides a method of inducing the apoptosis of cancer cells by the use of active vitamin D compounds, and includes a method for treating cancer by regressing tumor cells by the use of active vitamin D compounds.
The foregoing, and other advantages of the present invention, are realized in one aspect thereof in a method of inhibiting angiogenesis associated with malignant cells, comprising treating the cells with an effective amount of a hypocalcemic vitamin D compound. The hypocalcemic vitamin D compound of the present invention include hypocalcemic vitamin D compounds having a hydrocarbon moiety substituted at the C-24 position on the sidechain of the molecule and having a hydroxyl group substituted in at least one of the C1, C24 or C25 positions.
The hypocalcemic vitamin D compound is an active vitamin D and is suitably represented by the formula (I) described hereafter. Suitable compounds of formula (I), are 1xcex1,24-dihydroxyvitamin D2, 1xcex1,24-dihydroxyvitamin D4, 1xcex1,25-dihydroxyvitamin D4, 1xcex1,25-dihydroxyvitamin D2, 1xcex1-hydroxyvitamin D2 and 1xcex1-hydroxyvitamin D4.
The effective or therapeutic amount of the 1xcex1-hydroxyvitamin D compound administrable in accordance with the present invention to patients in need on a daily basis per kilogram of body weight ranges from 0.01 xcexcg/kg/day to 2.0 xcexcg/kg/day.
In another aspect of the invention, the apoptosis of cancer cells is accomplished by a method comprising, administering to patients an effective amount of a hypocalcemic vitamin D compound to induce the apoptosis of cancer cells.
In yet another aspect of the invention, a method for treating cancer by regressing tumor cells is disclosed, comprising administering to patients an effective amount of a hypocalcemic vitamin D compound to induce the regression of cancer cells.
In accordance with the present invention, when effective amounts of the hypocalcemic vitamin D compounds are administered to patients with cancer or neoplasms, the proliferative activity of the abnormal neoplastic cells is inhibited or maintained, and cell differentiation is induced, promoted or enhanced, with significantly less hypercalcemia and hypercalciuria than is observed after the same amount of an activated vitamin D3 (e.g., 1xcex1xe2x80x94OH D3, 1xcex1,25xe2x80x94(OH)2 D3) is administered in previously known formulations. Thus, the compound in accordance with the present invention has an improved therapeutic index relative to active forms of vitamin D3 analogues. Furthermore, the compounds of the present invention can be administered in doses significantly higher than that of active vitamin D3 analogs due to their lower calcemic effect.
Accordingly, another aspect of the invention is a method of treating human cancer comprising administering to a subject who has cancer an effective amount of active vitamin D compound which has, attained through metabolism in vivo, a vitamin D receptor (VDR) binding affinity substantially equivalent to the binding affinity of 1xcex1,25-dihydroxyvitamin D3 and a hypercalcemia risk substantially lower that that of 1xcex1,25-dihydroxyvitamin D3, to decrease or stabilize the cellular abnormal proliferative activity of the cancer.
For treatment for malignant conditions in accordance with the present invention, the active vitamin D is suitably administered alone as an active ingredient in a pharmaceutical composition, or is co-administered with an anticancer agent.
Further, included within the scope of the present invention is the co-administration of a hypocalcemic vitamin D compound with a cytotoxic or anticancer agent. Such agents suitably include antimetabolites (e.g., 5-fluoro-uracil, methotrexate, fludarabine), antimicrotubule agents (e.g., vincristine, vinblastine, taxanes such as paclitaxel, docetaxel), an alkylating agent (e.g., cyclophasphamide, melphalan, biochoroethylnitrosurea, hydroxyurea), platinum agents (e.g. cisplatin, carboplatin, oxaliplatin, JM-216, CI-973), anthracyclines (e.g., doxrubicin, daunorubicin), antibiolitics (e.g., mitomycin, idarubicin, adriamycin, daunomycin), topoisomerase inhibitiors (e.g., etoposide, camptothecins) or any other cytotoxic agents. (estramustine phosphate, prednimustine).
It is anticipated that the active vitamin D compounds used in combination with various anticancer drugs can give rise to a significantly enhanced cytotoxic effect on cancerous cells, thus providing an increased therapeutic effect. Specifically, as a significantly increased growth-inhibitory effect is obtained with the above disclosed combinations utilizing lower concentrations of the anticancer drugs compared to the treatment regimes in which the drugs are used alone, there is the potential to provide therapy wherein adverse side effects associated with the anticancer drugs are considerably reduced than normally observed with the anticancer drugs used alone in larger doses. Possible dose ranges of these co-administered anticancer agents are about 0.1 to 20 mg/kg/day.
Also included within the scope of the present invention is the co-administration of effective dosages of a hypocalcemic vitamin D compound in conjunction with administration of hormones or other agents, e.g., estrogens, which are known to ameliorate bone diseases or disorders. For example, prostate cancer often metastasizes to bone, causing bone loss and associated pain. Such bone agents may include conjugated estrogens or their equivalents, calcitonin, bisphosphonates, calcium supplements, cobalamin, pertussis toxin and boron.
In another aspect, the invention is a pharmaceutical composition which includes an anticancer agent which is an active vitamin D compound; an agent selected from the group consisting of (i) an anticancer agent, (ii) a bone agent, and combinations thereof; and a physiologically acceptable carrier.
Other advantages and a fuller appreciation of specific adaptations, compositional variations, and physical attributes will be gained upon an examination of the following detailed description of preferred embodiments, taken in conjunction with the appended claims.